Figure 1: A typical case of orbital IgG4-related disease. A 72-year-old man with bilateral upper eyelid swellings that developed over a one-year period (a). There was a 10-year history of chronic rhinosinusitis, and the patients had undergone surgical treatments. On examination, his best-corrected visual acuity was 20/20 OD and 20/25 OS. Computed tomography showed enlargements of both lacrimal glands (b), enlargement of several of the left extraocular muscles (c), and infiltrative lesions in the ethmoid and maxillary sinuses. However, his ocular movements were unrestricted, and diplopia was not observed. He had elevated levels of serum IgG (4205 mg/dL; normal range: 870–1700 mg/dL) and serum IgG4 (1190 mg/dL; normal range: 4.8–105 mg/dL). These infiltrative lesions decreased in size after administration of oral prednisolone (30 mg) with a slow taper.